In Emerging Adulthood, Perceived Stress is Linked to Poor Diet Quality

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Sensitivity of Micromachined Joule-Thomson Cooler to Clogging Due to Moisture

A major issue in long-term operation of micromachined Joule-Thomson coolers is the clogging of the microchannels and/or the restriction due to the deposition of water molecules present in the working fluid. In this study, we present the performance of a microcooler operated with nitrogen gas with different moisture levels. Relatively low-purity nitrogen gas (5.0) is supplied from a gas bottle and led through a filter to control the moisture level. The filter consists of a tube-in-tube counter flow heat exchanger (CFHX) and a heat exchanger that is stabilized at a certain temperature by using a Stirling cooler. The set-point temperature determines the moisture level at the exit of the heat exchanger. It is found that the moisture level has influence on the mass-flow rate during the cool down. Once the microcooler reaches the set cold-end temperature, the main deposition area shifts into the CFHX and the moisture level at the restriction is almost independent on the inlet moisture level of the microcooler. The moisture level at the restriction increases with the increasing cold-end temperature when the cold-end temperature is lower than the saturation temperature of the water in the nitrogen gas. Higher cold-end temperature results in higher clogging rate

A Passive, Adaptive and Autonomous Gas Gap Heat Switch

We report on the development of a heat switch for autonomous temperature control of electronic components in a satellite. A heat switch can modulate when needed between roles of a good thermal conductor and a good thermal insulator. Electronic boxes on a satellite should be maintained within a typical optimum temperature range of 260 to 310 K. The heat sinking is usually by means of a radiator. When the operating temperature of the electronic box increases beyond 310 K, a good contact to the radiator is desired for maximum cooling. On the other hand, when the satellite is in a cold dormant state, the electronics box should be heated by the onboard batteries. In this state a weak thermal contact is desired between the electronic box and the heat sink. In the present study, we are developing a gas gap heat switch in which the sorber material is thermally anchored to the electronic box. A temperature change of the electronic box triggers the (de-)sorption of gas from the sorber material and subsequently the gas pressure in the gas gap. This paper describes the physical principles and the current status of this technology. This approach can be extended to cryogenic temperature rang